1. Field of the Invention
This invention relates to mechanisms for raising heavy loads upwards from the cargo bed of a truck, using actuators operated by hydraulic power, or similar force-producing means. More particularly, the invention relates to a hydraulic lift mechanism which may be used to raise heavy loads such as a camper shell, tool compartment box or the like, above the bed of a truck to allow access to the truck bed, and lower the lifted portion to a low profile position as desired.
2. Description of Background Art
Pickup trucks, and to a lesser extent, small flatbed trucks, are used extensively as recreational vehicles. Such vehicles are often modified by the installation of an enclosure installed in the cargo area of the truck, the enclosure covering sleeping, cooking, toilet facilities and the like. The enclosures are commonly called camper shells, the name deriving from the intended use of the vehicle and the shape of the enclosure, which is usually that of an elongated, inverted box or shell.
When a vehicle equipped with a camper shell is in transit, it is desirable to have the vertical extension of the shell above the bed of the truck at a minimum. Minimum extension affords minimum wind resistance. Excessive wind resistance presented by high-profile camper shells can substantially reduce the gas mileage and operating efficiency of vehicles so equipped. Also, the wind resistance afforded by high profile camper shells can make a vehicle dangerously unstable in high cross winds.
From the comments made above, it is evident that low-profile camper shells are desirable when the vehicle equipped with the camper shell is in transit. However, when the vehicle has reached an intended destination such as a camp site, it would be desirable to have sufficient vertical clearance in the space between the camper shell roof and the bed of the truck on which the shell is mounted to permit adults to walk comfortably under the camper shell, without having to stoop. Thus, it would be desirable to have a camper shell which may be raised from a low-profile transit position to a higher clearance use position at a camp site, and readily returned to the low-profile position when departing from the camp site.
In apparent recognition of the desirability of having an extensible roof for the living quarters of recreational vehicles, a number of patents disclose such apparatus. These include the following U.S. Pat. Nos.:
Borskey, 3,582,130, June 1, 1971, Vehicle With Retractable and Extensible Roof Assembly. PA1 Borskey, 3,770,314, Nov. 6, 1973, Vehicle With Retractable and Extensible Roof Assembly. PA1 Gogush, 3,924,889, Dec. 9, 1975, Elevating Mechanism For The Roof Or Tops Of Vans And The Like. PA1 McIntosh, 4,603,901, Aug. 5, 1980, Liftable Top For Pickup Trucks. and PA1 German patent 2,840,487, Weinsberg, Mar. 27, 1980, Elevating Roof Drive Mechanism For Motor Carava. PA1 Traficant, 3,891,108, June 24, 1975, High Lift Mechanism. PA1 Luebke, 4,092,011, May 30, 1978, Lift Mechanism For A Truck. PA1 Oswald, 4,526,344, July 2, 1985, Auxiliary Lift Adapter. PA1 Tominaga, 4,556,198, Dec. 3, 1985, Height Adjusting Lifter For Hospital Bed.
U.S. Pat. Nos. disclosing the use of scissors jack-like lifting mechanisms include:
The present invention was conceived of to provide a lift mechanism for camper shells which can be readily attached to the bed or cargo box of a flat bed or pick-up truck without obstructing any useable space within the shell, whether the shell is in an elevated, use position or a lowered, transit position.